thanks for reply stryd, yes I do more reading than posting. ;) For example I coudln`t manage to insert a gif into this post. instead please follow this hyperlink (screenshot of midiox midi monitors, sending a preset bank. looped rx-tx at pic socket) http://www.benjie.de/public/mididata.GIF Am I wrong or does this mean diode, optocoupler and resitors are ok? the rest of the test: TestProg1: Bootloader seems to be ok, because i am getting request messages every 2 seconds Test core1: crystal is there Test core3: tested but will be tested over and over again :) test core 4: all 5.287 V test core 5 all 5.28 V test core 6 switched plugs but then midi loop doesn't work any more test core 7 looks ok to me: black ring towards pin 1 of ic2 test core 8 resitor values mesured, ok test core 10 like test 6 test core 11 request message seems correct F0 00 00 7E 40 ... F7 I am using the optimized c64 psu. I took out the 7805 from the core and bypassed outer pins to connect the 2200uf to the 5V test out1 haven't done it yet, because I am receiving this request, so the out seems to be fine test out2 same like out1 ----------------- test in 1 checked but will be checked again test in 2 like test core 6 test in 3-5 pls. look at first post test in 6 and 7 as far as i can see optocoupler is working (didint make the tests) test inout1 working test sw1 und sw1 i dont have no burner :'( ------------------------- bless lötmann